Is all this at 1st level? If yes, how does it develop as the fighter levels up?
Which levels things out for combat purposes, good to hear. NPCs, commoners, non-adventurers etc., on the same system?
Yes all is at 1st level. It is part of chargen. To summarize my game, your character is the sum of your backgrounds. You start at age 5, choose backgrounds which have a variable aging until your character is between age 15-25. Sometimes you might be older than 25 depending on choices. For example street urchin ages you two years, magician apprentice ages you seven.
As you play you gain both experience points which grant level abilities, and improvement points 1 for every 1000 experience. Every level grants an ability, improvement points are used to increase attributes and skill ratings.
There are four groups of level abilities. Social boons that anyone can choose, divine miracles for those with a divine background, arcane abilities for those with an arcane background, and Combat maneuvers/tricks. Admittedly the combat maneuvers/tricks was the most difficult to create as they apply to purely mundane characters; fighter types and thief types.
Quick examples of each level ability
Social boon: High functioning alcoholic, poison resistance (choose one)
Divine: Druid shape shifting form, summoning servant of deity, banish fiends
Arcane: Higher magic order (spell slots), meta magic ability
Combat: Fancy footwork, kick or trip foe as situation warrants, Favored weapon increases weapon skill for a single weapon, Distracting sound; cause foe to look wrong way gain bonus on attack
Commoners use a simpler system for their skills, 3 skill points per year of age above 5. These are always non casters with very limited weapon skills. The 16 year old inn keeper's daughter can cook, brew beer, sew and stitch clothing, fight with improvised weapon (frying pan, rolling pin) if necessary as last resort.